In a specimen process of, for example, an examination or analysis of a specimen such as blood or serum, a specimen container is held in a holder in an upright state and conveyed, and various processes are performed by various detection devices disposed on a convey path of the holder. In such a specimen process, a cap is attached for closing the opening of the specimen container. For example, in the state in which the specimen container is held, a cap formed of a material with high flexibility, such as rubber, is pushed in the opening of the specimen container, and thereby the cap is attached (As described in Jpn. Pat. Appln. KOKAI Publication No. 6-239389). In addition, a screw-type cap has been proposed in order to enhance sealing performance. The sealing performance of the screw-type cap deteriorates if the fastening of the screw-type cap is loose. Thus, there is a demand for a technique for exactly attaching the cap.